1. Field of the Invention
The present invention relates generally to a lapping method and lapping apparatus, and more particularly, to a lapping method and lapping apparatus used in the manufacture of slider-mounted composite magnetic heads.
2. Description of Related Art
For clarity of explanation, a description will first be given of the structure of a slider-mounted composite magnetic head used in disk drives for recording information to and/or reproducing information from a recording medium.
FIGS. 1A and 1B are diagrams for explaining a slider-mounted composite-type magnetic head. FIG. 1A shows an expanded cross-sectional view of a portion of a slider-mounted composite magnetic head 1. The slider-mounted composite magnetic head 1 has a composite magnetic head 11 at a tip of a ceramic slider 2. The composite magnetic head 11 has a magnetoresistive head element 3 for reproducing information and an inductive head element 4 for recording information.
As shown in FIG. 1B, the magnetoresistive head element 3 is a thin film comprised of a magnetoresistive film 5 provided on a lower side of the head 1 that faces laterally, with a pair of conductive film terminals 6a, 6b connected to either end of the magnetoresistive film 5. The resistance of the magnetoresistive film 5 changes depending on the external magnetic field to which it is exposed and a sense current is sent through the magnetoresistive film 5. Thus, when the head 1 scans a disk, the resistance of the magnetoresistive film 5 changes according to the magnetization of the disk tracks T over which the head 1 scans and thus a voltage across the conductive film terminals 6a, 6b also changes, with the result that the information recorded on the disk tracks T is read out as changes in voltage.
The inductive head element 4 is also a thin film, with a lower electrode 7, an upper electrode 8, and a coil 9 located between the lower electrode 7 and the upper electrode 8. When the head 1 scans the disk, signals of information to be written onto the disk are supplied to the coil 9 and a magnetic field is extruded from a lower magnetic gap 10 between the lower electrode 7 and the upper electrode 8. This magnetic field writes information to the tracks T of the disk.
In manufacturing the slider-mounted composite magnetic head 1 having the structure described above, it is desirable that the resistance of the magnetoresistive film 5 be the same or nearly the same for all such heads so fabricated. Generally, as will be described in detail later, this uniformity of resistance is achieved by lapping so that a thickness or height h of the magnetoresistive film 5 is the same for all slider-mounted composite magnetic heads 1, such that the heads 1 achieve a predetermined resistance value.
Next, a description will be given of the process of manufacturing the above-described slider-mounted composite magnetic head 1, with reference to FIGS. 2A, 2B, 2C, 2D, 3A, 3B, 4A, 4B and 4C.
FIGS. 2A, 2B, 2C and 2D show initial steps in a process of manufacturing the slider-mounted composite magnetic head 1. FIGS. 3A and 3B show further steps in the process of manufacturing the slider-mounted composite magnetic head 1 shown in FIGS. 2A, 2B, 2C and 2D. FIGS. 4A, 4B and 4C show remaining steps in the process of manufacturing the slider-mounted composite magnetic head 1 shown in FIGS. 3A and 3B.
Generally, the manufacture of such heads involves the following steps, in the following order: Patterning, dicing, attaching, grinding, lapping, dicing, and peeling.
Initially, a pattern is formed on a ceramic wafer 20 as shown in FIG. 2A using thin film technology. Composite magnetic heads 11 and ELG (Electronic Lapping Guide) elements are laid down in alternate sequence as shown in FIGS. 2B and 2C. The wafer 20 has a thickness corresponding to a length a of the slider. The wafer 20 is then diced and, as shown in FIG. 2B, a multiplicity of row bars 22 are obtained. The row bar 22, which as can be appreciated is in the shape of a bar, has a composite magnetic head 11 and an ELG element 21 laid down in alternate sequence, together with a margin portion 23 to be ground or lapped. It should be noted that the magnetoresistive film 5 and the ELG element 21 are both formed by thin-film technology patterning, and the magnetoresistive film 5 and ELG element 21 are positioned with a high degree of accuracy.
Next, as shown in FIG. 3A, the row bar 22 is attached to a tip of a transfer tool 30 using wax. A multiplicity of concave portions 31 are formed along the tip of the transfer tool 30. The row bar 22, as shown in FIG. 3B, is attached so that the ELG elements 21 are disposed opposite the concave portions 31. The concave portions 31 are formed so as not to interfere with the dicing step to follow. The transfer tool 30 is fixedly mounted to a printed circuit board 32. The ELG elements 21 and terminals on the printed circuit board 32 are connected, or bonded, by wire 33 as shown in FIG. 3B, thus connecting the ELG elements 21 and the printed circuit board 32 electrically.
Next, the transfer tool 30 to which the row bar 22 is attached is set to a grinding machine not shown in the diagram and the row bar 22 is ground down to a point indicated by a dashed line 34 in FIG. 3B.
Next, the transfer tool 30 is removed from the sander and set to a lapping device not shown in the drawing in order to lap the ground surface of the row bar as shown in FIG. 4A. As lapping progresses, the width, that is, the height h of the magnetoresistive film 5 gradually decreases, as does the height of the ELG elements 21, and, accordingly, the magnetic resistance MRh gradually increases. Moreover, because the magnetoresistive film 5 and the ELG 21 are positioned with great precision, it is possible to know the height of the magnetoresistive film 5 from the condition of the ELG elements 21. Therefore lapping is conducted while monitoring the magnetic resistance MRh of the ELG 21. When this magnetic resistance MRh of the ELG elements 21 reaches a target value, lapping is discontinued. At this point in time the height h of the magnetoresistive film 5 should have reached its target value. This lapping process is very precise, that is, on the order of sub-microns.
Next, the transfer tool 30 is removed from the lapping device and set to a dicing device not shown in the diagram and, as shown in FIG. 4B, the lapped row bar 22 is cut through to the interior of the concave portions 31 using a dicing saw 35, thus cutting out the row bar 22 ELG elements 21. In so doing, the row bar 22 is separated into a plurality of heads 1.
Finally, the transfer tool 30 is heated so as to melt the wax holding the row bar 22 onto the tip of the transfer tool 30. In so doing, the plurality of heads 1 into which the cut row bar 22 has been divided peel off from the transfer tool 30, resulting in fully formed slider-mounted composite magnetic heads 1 having a height b of approximately 0.3 mm and a length a of approximately 1.2 mm.
It will be appreciated by those skilled in the art that the production process described above is also used to fabricate giant magnetoresistive heads, or GMR heads, having a plurality of different film layers in contrast to the single layer of the magnetoresistive film characteristic of magnetoresistive heads described above.
A description will now be given of the conventional art.
FIG. 5 shows a perspective view of a conventional lapping device for lapping a row bar, as shown for example in Japanese Laid-Open Patent Application No. 10-286767. As shown in the diagram, this conventional lapping device 40 has a base 41, a rotary plate 42 that rotates in a direction indicated by arrow A in the diagram, an arm assembly 44 supported by a shaft 43, an oscillating mechanism 45 that swings the arm assembly 44 about the shaft 43 in directions indicated by double-headed arrow B in the diagram, and a ring 46 that rotates in a direction indicated by arrow C in the diagram so as to spread a slurry across an upper surface of the rotary lapping plate 42. Additionally, the conventional lapping device 40 also has a detachable adapter 50.
FIG. 6 shows the rotary lapping plate and associated parts depicted in FIG. 5. FIG. 7 shows a side view of the assembly shown in FIG. 6, including an unload mechanism 51 and an unload block 52 to be described later. FIG. 8 shows a schematic view of an adapter portion.
The transfer tool 30A having the ground row bar 22 is mounted on the adapter 50 as shown in FIGS. 6, 7 and 8. As can be appreciated from the drawings, particularly FIG. 8, the adapter 50 has a generally paddle-shaped form. Further, the adapter 50 is mounted on the arm assembly 44. By oscillating the arm assembly 44, the ground row bar 22 is moved along an upper surface of the rotary lapping plate 42 in a direction of a radius of the rotary lapping plate 42 at a rate of approximately one cycle every 10 seconds. It should be noted that the rotary lapping plate 42 is at this time rotating at approximately 15 rpm.
When the resistance MRh of the ELG elements reaches a target value, the unload mechanism 51 is activated and the unload block 52 is moved in a direction indicated by arrow D in FIG. 7. The movement of the unload block in the direction of arrow D forces the adapter 50 upward to a position indicated by the double-dot-and-chain line in FIG. 7, which in turn lifts the lapped row bar 22 off the rotary lapping plate 42, completing the lapping operation.
However, the lapping system described above has several disadvantages.
First, the manner in which the lapped row bar 22 is unloaded from the rotary lapping plate 42 degrades the precision of the lapping.
In the finished product, the lapped surface of the row bar 22 becomes an air-bearing surface that floats above the disk-like recording medium, so the rotary lapping plate 42 must not leave any scratches or scars on this surface.
However, when the row bar 22 reaches the end of its arcuate oscillation, that is, when the row bar 22 attains positions Q1 and Q2 at the end of its swing as indicated in FIG. 6, the row bar 22 naturally stops at such positions. If the row bar 22 is unloaded from the rotary lapping plate 42 at these positions at which the motion of the row bar 22 has terminated, then it is possible that the rotary lapping plate 42 will scratch the lapped surface of the row bar 22 in the interval of time after which the motion of the row bar 22 has stopped but before the row bar 22 is unloaded. For this reason, then, unloading is restricted to an area near a point P as indicated in FIG. 6, that is, near a middle of the arc through which the row bar 22 travels across the upper surface of the rotary lapping plate 42.
As a result, however, it is not possible to promptly unload the row bar 22 at the point in time at which the resistance of the ELG elements 21 attains the target value because the row bar 22 may be out of position, that is, the row bar 22 may be near positions Q1 and Q2, thus forcing a delay of up to several seconds before the row bar 22 can be unloaded. During this interval the row bar 22 continues to be lapped beyond the level required, thus degrading the precision of the lapping process. With recent advances in recording medium density technology, excess-lapping deviations of even one micron have become unacceptable.
Second, the conventional lapping system as described above depends too greatly on the skill of the human operator.
As shown for example in FIG. 7, when beginning lapping, the operator must mount the transfer tool 30 (to which the ground row bar 22 has been attached) onto the adapter 50 and then mount the adapter 50 onto the arm assembly 44.
However, deviations arise in the mounting of the adapter 50 onto the arm assembly 44, and such differences result in unevenness in the contact of the row bar 22 with the upper surface of the rotary lapping plate 42. These deviations can damage the soft tin surface of the rotary lapping plate 42 and degrade the precision of the lapping itself.
Third, the working life of a ceramic stopper 53 on the arm assembly 44 is short.
Specifically, the arm assembly 44 continues to oscillate even after lapping has been completed, keeping the ceramic stopper 53 at the tip of the arm assembly 44 in continuous abrasive contact with the rotary lapping plate 42, thus shortening the useful life of the stopper 53.
Fourth, the lapping process according to the lapping system as described above can be unstable. The extent to which the stopper 53 is abraded creates an unbalance at the tip of the arm assembly 44 during lapping which may cause the tip of the arm assembly 44 to vibrate, disrupting the stability of the row bar 22 and degrading the precision of the lapping.
Accordingly, it is a general object of the present invention to provide an improved and useful lapping method and lapping apparatus, in which the above-described disadvantages are eliminated.
The above-described object of the present invention is achieved by a lapping method including a step of moving a substantially bar-shaped workpiece in a radial direction of a surface of a rotary lapping plate while simultaneously oscillating the workpiece pivotally about a central point in a longitudinal direction of the workpiece in a plane parallel to the surface of the rotary lapping plate.
According to the invention described above, the workpiece can be maintained in constant motion across the surface of the rotary lapping plate. As a result of this constant motion it is more difficult for the rotary lapping plate to scratch or scar the lapped surface of the row bar, so the degree of precision with which the row bar is lapped can be improved.
Additionally, the above-described object of the present invention is also achieved by a lapping apparatus comprising:
a rotary lapping plate;
an arcuate movement mechanism returnably moving a substantially bar-shaped workpiece repeatedly in a radial direction of a surface of the rotary lapping plate; and
an oscillating mechanism oscillating the workpiece pivotally about a central point in a longitudinal direction of the workpiece in a plane parallel to the surface of the rotary lapping plate,
the oscillating mechanism being supported on and by the arcuate movement mechanism.
According to the invention described above, the workpiece can be maintained in constant motion across the surface of the rotary lapping plate. As a result of this constant motion it is more difficult for the rotary lapping plate to scratch or scar the lapped surface of the row bar, and thus the degree of precision with which the row bar is lapped can be improved.
Additionally, the above-described object of the present invention is also achieved by a lapping apparatus comprising:
a rotary lapping plate;
an oscillating mechanism oscillating a workpiece pivotally about a central point of the workpiece while maintaining the workpiece in sliding contact with an upper surface of the rotary lapping plate, the mechanism having a stopper that slidingly contacts the upper surface of the rotary lapping plate; and
a loading/unloading mechanism that moves the stopper of the oscillating mechanism in a loading direction toward the rotary lapping plate and an unloading direction away from the rotary lapping plate.
According to the invention described above, the stopper is removed from contact with the rotary lapping plate, thereby preventing unnecessary abrasion of the stopper and thus extending the useful life of the stopper.
Additionally, the above-described object of the present invention is also achieved by a lapping apparatus comprising:
a rotary lapping plate;
an oscillating mechanism oscillating a workpiece pivotally about a central point of the workpiece while maintaining the workpiece in sliding contact with an upper surface of the rotary lapping plate, the mechanism having a stopper that slidingly contacts the upper surface of the rotary lapping plate; and
a wiper unit having a blade portion that contacts the upper surface of the rotary lapping plate,
the wiper unit being activated to remove a rough slurry supplied to the upper surface of the rotary lapping plate before a smooth slurry is supplied to the upper surface of the rotary lapping plate.
According to the invention described above, by activating the wiper unit to after the rough slurry has been applied but before the smooth slurry is applied improves the precision of the lapping.